Postgraduate work at University of Chicago; early work in spectroscopy using the Fabry-Perot interferometer; studies of e/m and hydrogen fine structure. Study at Universitt̃ M nchen with Arnold Sommerfeld and the development in electron spin research in the 1930s; work with and impressions of Werner Heisenberg and others. Later work in solid state; interest in quantum statistics and its relation to statistics of ensemble. Discussion of major problems in modern physics; teaching methods and responsibilities, administration and research, solid state developments.